Abstract

Scombroid poisoning is a form of toxicity caused by the ingestion of spoiled dark-flesh fishes, mainly of the scombroid family.
The clinical picture is secondary to histamine toxicity, manifested as flushing, headache, palpitations, and abdominal cramps.
The diagnosis is established on the basis of these typical clinical manifestations and fish-ingestion history. We report a
case of a man with scombroid poisoning. He was diagnosed after presentation of two similar patients with the same epidemiological
history.

Clinical synopsis

Figure 1

Figure 2

Figure 1. Diffuse reddening of the face, neck and upper chest and back

Figure 2. Complete resolution of the eruption after 1 hour, without treatment

This 25-year-old man presented with this cutaneous eruption that appeared suddenly half an hour before. He complained of an
associated burning sensation as well throbbing headache and dizziness. The eruption started 1 hour after lunch. He reported
having eaten a full serving of a tuna dish. One hour after presentation and without any treatment the eruption resolved. Two
additional cases presenting a similar clinical picture and having eaten tuna from the same restaurant were observed during
the following days. On the basis of the clinical manifestations and the epidemiology of three cases having eaten tuna in the
same restaurant, a diagnosis of flushing syndrome secondary to scombroid fish poisoning was made.

Discussion

Scombroid poisoning, also known as histamine fish poisoning (HFP), is nowadays the most common form of fish toxicity. First
reported in 1830 by Henderson [1], it is a form of toxicity attributed to ingestion of spoiled dark-flesh fishes mainly of the scombroid family, which includes
tuna, bonito, mackerel and albacore. Other non-scombroid fishes, such as mahimahi, kahawai, Japanese sauri, amberjack, sardines,
pilchards, anchovies, and herring, among others, have also been implicated [2, 3, 4]. Most of the cases reported have been related to consumption of fresh fish. However, Predy et al. described a case associated
with ingestion of canned tuna [5]. Therefore, food preparation, including cooking, does not destroy the toxins.

The mechanism of toxicity in scombroid poisoning remains unclear. Inappropriate refrigeration and manipulation of fish can
lead to bacterial decomposition. It is postulated that histidine, normally present in high concentration in the muscle of
dark-meat fishes, is decarboxylated to histamine by bacteria (species implicated are Proteus morgagni, Klebsiella pneumoniae, Clostridium perfringens, Shigella dysenteriae and certain strains of Escherichia coli and Aerobacter aerogenes) [2]. The decarboxylation of histidine present in the fish is accelerated at 20-30° C.

Histamine is considered toxic when levels are higher than 100 mg per kg. The Food and Drug Administration uses 50mg per 100g
or more as a hazardous level in tuna [6]. However, because the ingestion of poisoning dose-equivalent histamine does not reproduce the symptoms, other factors in
combination with histamine produce the illness. For instance there may be a synergy with other biologically active amines
[7].

The diagnosis of scombroid fish poisoning is usually established on the basis of a characteristic clinical picture and evolution.
The patients commonly relate a history of peppery or sharp taste, followed by oral burning or blistering. Signs and symptoms
consistent with scombroid fish poisoning, which resemble histamine intoxication, begin 30 to 40 minutes after the fish ingestion.
They consist of flushing, headache, palpitations, tachycardia, abdominal cramps, diarrhea, dizziness, burning of gingivae
or throat, dryness of the mouth, nausea, vomiting, urticaria, and angioneurotic edema. The flushing is one of the most frequent
symptoms, and it resembles a sunburn with sharply demarcated borders, involving the upper trunk, arms and face. In severe
cases, bronchospasm, respiratory distress, and hypotension (vasodilatory shock) have been also reported [2, 4, 9]. The mean duration of the symptoms is 4 hours; however, some cases have persisted up to 8 hours. The observation of a clinical
picture similar to histamine toxicity occurring after a meal should alert the clinician to the possibility of scombroid poisoning.

Laboratory tests can demonstrate a high level of histamine in the patient's urine and plasma, as well as a high concentration
of histamine in the fish tissue [8]. However, measurement of plasma histamine levels is often not available in clinical laboratories, and urine histamine levels
can be falsely elevated.

The differential diagnosis includes flushing secondary to other foods: Chinese food (monosodium glutamate), preserved meats
(sodium nitrites), pepper (capsaicin), some cheeses (Swiss, Gouda, Cheddar, Gruyere, and Cheshire), soy products, and wines
rich in amines, especially for patients taking monoamine oxidase inhibitors. Finally, a similar illness is ciguatera fish
poisoning, attributed to eating fish that contain toxins produced by the marine microalgae Gambierdiscus toxicus, usually in the tropic regions of the world. It presents 2-5 hours after ingestion, with nausea, vomiting, and neurological
symptoms, such as tingling fingers or toes. Severe cases can experience a cold-to-hot sensory reversal such that cold objects
feel hot and hot objects feel cold. It usually lasts a few days, but severe neurological disorders may persist for months
and sometimes for years.

Because symptoms of scombroid poisoning usually resolve spontaneously within a few hours, the treatment is usually symptomatic,
and often not necessary. Some authors recommend administering a combination of H1 and H2 antihistamines. In exceptionally
severe cases, adrenaline together with intravenous fluids may be indicated when airway compromise or refractory hypotension
is present. Steroids are thought to be unhelpful and may prolong the disease [10]. Because the histamine reaction is non-allergic, patients will be able to eat the same type of fish at a later time.